Thread rolling tool

ABSTRACT

The invention relates to a thread rolling tool for rolling and/or repairing a thread, comprising a clamping device to be fastened to a pipe end, and at least one profiled roll for rolling a thread into the pipe end or repairing a thread at the pipe end. According to the invention, the at least one profiled roll tapers in a direction in which the profiled roll advances such that a tapered, in particular a conical, thread can be rolled into the pipe end.

The invention relates to a thread-rolling tool for rolling and/orrepairing a thread, with (a) a clamping jig for fastening to a pipe endand (b) at least one profile roll for rolling a thread into the pipe endor for repairing a thread at the pipe end.

Such a thread-rolling tool is known, for example from DE 10 2012 004 701A1. A disadvantage of such a thread-rolling tool is that it is suitableonly for cylindrical threads. In other words, conical threads cannot berolled with such a tool.

The task of the invention is to propose a thread-rolling tool that issuitable for rolling and/or repairing a tapering, especially a conicalthread.

The invention accomplishes the task by a thread-rolling tool of theclass in question, in which the at least one profile roll tapers in afeed direction of the profile roll, so that a tapering, especially aconical thread can be rolled into the pipe end.

The invention is based on the knowledge that a conical thread can beproduced when a conical profile roll is used. If this profile roll onthe pipe end that runs out taperingly, especially conically, the profileroll comes into contact with the pipe end over a large portion of itsshell surface. By rotating the profile roll on a helical path around thelongitudinal axis of the pipe end, the profile roll cuts a thread intothe pipe end. The envelope contour of the profile roll, i.e. the contourof the profile roll without the grooves, is therefore preferably shapedin a manner complementary to the contour of the tapering thread to beproduced.

It is particularly favorable when the profile roll has a conical basicstructure, meaning that the groove crests lie on a conical surface. Inthis way a conical thread is obtained.

In the context of the present description, the clamping jig will beunderstood as a jig by means of which the thread-rolling tool can befastened at the pipe end. In particular, the clamping jig is designedfor insertion into the pipe at the pipe end and for fastening of thethread-rolling tool at the pipe end by enlarging the outside diameter ofthe clamping jig, for example by radial outward movement of clampingelements. The clamping jig may be actuated mechanically, pneumaticallyor hydraulically. In principle, the clamping jig may also be based on adifferent clamping principle; for example it may represent afreeze-clamping chuck. However, this is frequently associated withincreased expense.

By the profile roll there will be understood a component by means ofwhich a thread can be rolled into the pipe end. Preferably the profileroll has a conical envelope contour, which means that the profile rollcan be produced by machining the profile into a conical portion in theportion provided with the profile used for rolling the thread.

By the feature that a thread can be rolled into the pipe end, it willalso be understood in particular that an already existing but damagedthread can be so modified by means of the thread-rolling tool that afunctionally effective thread is obtained.

Preferably the profile roll is pitchless. This has the advantage thatthe thread can be rolled and/or repaired with particularly high processreliability and in simple manner.

According to a preferred embodiment, the thread-rolling tool comprises aroll holder, on which the at least one profile roll is fastened and bymeans of which the at least one profile roll can be so guided helicallyaround the pipe end that the at least one profile roll rolls a threadinto the pipe end. By the feature that the profile roll can be guidedhelically around the pipe end, it will be understood that it can beguided on a helical path, which in particular is non-tapering, aroundthe longitudinal axis of the pipe end. Certainly it is possible that thehelical path tapers, which means that its diameter becomes smaller withincreasing distance along the longitudinal axis, but this is notrequired. In addition, it is possible that the helical path widens.However, the thread-rolling tool is constructed particularly simply whenthe roll holder moves on a helical path that neither tapers nor flaresaround the longitudinal axis.

Preferably the roll holder is coupled by means of a thread with theclamping jig, so that a rotation of the roll holder around the pipelongitudinal axis of the pipe end leads to an axial movement of the rollholder along the pipe longitudinal axis. This represents a particularlysimple and in addition process-reliable way of moving the roll holder ona helical path around the pipe longitudinal axis. It is particularlyfavorable when at least one of the threaded partners is made of hardenedsteel or of another hard material with a Rockwell hardness of at least45 HRC. Thus the forces developed during rolling of the thread can beabsorbed without this leading to excessive wear.

According to a preferred embodiment, the thread-rolling tool comprisesat least one second profile roll, which is so fastened to the rollholder that the second profile roll, during rotation of the roll holderaround the pipe longitudinal axis, rolls at least partly in groovesrolled by the first profile roll and that, in operation, it generates,in a direction at least partly opposed to a first passive force thatacts on the first profile roll, a second passive force. The secondprofile roll therefore leads to a smaller torque that must be applied onthe thread-rolling tool in order to roll the thread.

Alternatively to the second profile roll, it is possible that thethread-rolling tool has a counter-element, which generates a secondpassive force directed at least partly opposed to the first passiveforce. In this case, however, significant frictional force easilydevelops, which reduces the attainable quality for the thread and whichgreatly increases the torque necessary for actuation.

The second profile roll is preferably pitchless. It is favorable whenthe profile rolls are similarly structured, at least in the profiledportion. In particular, the profile rolls are preferably identical. Withrespect to an axis of rotation of the first profile roll, the profile ofthe second profile roll is offset relative to the profile of the firstprofile roll.

It is favorable but not required when at least one of the profile rollsis mounted to be axially displaceable. Preferably the first profile rollis mounted to rotate around a first profile roll axis of rotation andthe second profile roll is mounted to rotate around a second profileroll axis of rotation, wherein the second profile roll axis of rotationforms an angle of 0° to 2° with the first profile roll axis of rotation.

According to a preferred embodiment, the first profile roll is mountedto rotate around a first profile roll axis of rotation and a firstoffset angle between the first profile roll axis of rotation (D14.1) andthe pipe longitudinal axis amounts to at most 2°, especially at most 1°.Preferably, however, the angle is quantitatively as small as possible.The pipe longitudinal axis corresponds to the axis of rotation aroundwhich the roll holder can be rotated.

The fact that the offset angle exists does not necessarily mean that thelongitudinal axis and the first profile roll axis of rotation intersect.The offset angle is calculated according to the mathematical rules forangle calculation from the direction vectors of the vectorialrepresentation of axis of rotation and longitudinal axis, wherein thedirection vectors are chosen in particular such that the offset angleamounts to at most 90°. The offset angle is always expressed positively,and so a theoretical angle of −0.5°, for example, between axis ofrotation and longitudinal axis is regarded as an offset angle of 0.5°.

Preferably the second profile roll is mounted to rotate around a secondprofile roll axis of rotation and a second offset angle between thesecond profile roll axis of rotation and the pipe longitudinal axisamounts to at most 2°, especially at most 1°.

Preferably the thread-rolling tool comprises at least one third profileroll, which is so fastened to the roll holder that the third profileroll, during rotation of the roll holder around the pipe longitudinalaxis, rolls at least partly in the grooves produced by the first profileroll or the second profile roll and that, in operation, it generates athird passive force, which together with the first passive force and thesecond passive force adds up vectorially to zero. In this way the threadcan be generated with a particularly small torque.

It is particularly favorable when the third profile roll is mounted torotate around a third profile roll axis of rotation and the thirdprofile roll axis of rotation forms a third offset angle of at most 2°,especially of at most 1° with the pipe longitudinal axis, whichcorresponds to the axis of rotation of the roll holder.

According to a preferred embodiment, the clamping jig has an actuatingconnecting piece, by means of which the clamping jig can be clamped andloosened and which extends in the direction of the pipe longitudinalaxis. In particular, the connecting piece is provided with a couplingstructure, for example a male hexagon structure or a hexagon socketstructure, so that the actuating connecting piece can be actuated with acomplementary tool.

The invention additionally accomplishes the task by a method forproducing or repairing a conical thread, with the steps of (i) fasteninga thread-rolling tool according to the invention onto a pipe end bymeans of the clamping jig and (ii) rotating the roll holder, wherein thethread moves the roll holder axially along a pipe longitudinal axis ofthe pipe end, so that the at least one profile roll moves helicallyaround the pipe longitudinal axis and rolls a conical thread into thepipe end or repairs the conical thread.

It is favorable when the pipe end runs out taperingly, especiallyconically. However, it is also conceivable that the pipe end does notrun out taperingly. In this respect it is advantageous to omit theproduction of the conical portion. It is disadvantageous that much morematerial must be shaped, which greatly increases the process forces.

According to a preferred embodiment, a thread is rolled with a threadwidth that corresponds at most to a profile roll width of a profileshell surface of the profile roll.

There are shown in:

FIG. 1 a perspective view of a thread-rolling tool according to theinvention,

FIG. 2 a section through the thread-rolling tool according to FIG. 1,

FIG. 3 a profile roll with a conical envelope body and

FIG. 4 a second perspective view of the thread-rolling tool.

FIG. 1 shows a thread-rolling tool 10, which has a clamping jig 12 aswell as a first profile roll 14.1, a second profile roll 14.2 and athird profile roll 14.3. The profile rolls 14 (reference symbols withoutnumerical suffix relate respectively to all corresponding objects) aremounted on a roll holder 16.

The profile roll 14.1 is mounted to rotate around a first profile rollaxis of rotation D14.1, the second profile roll 14.2 can rotate around asecond profile roll axis of rotation D14.2, the third profile roll 14.3can rotate around a third profile roll axis of rotation D14.3. The threeaxes of rotation D14.1, D14.2 and D14.3 form an angle of at most 2°,especially at most 1° pairwise with one another.

The clamping jig 12 is designed for fastening to a pipe end 18 and forthis purpose it has clamping elements 20.1, 20.2, . . . , which can bemoved radially outward via a clamping cone 23. The clamping cone 22 hasa thread—not visible in FIG. 1—and, by turning of an actuatingconnecting piece 24, can be thrust in axial direction corresponding to apipe longitudinal axis L relative to the clamping elements 20.

The clamping jig 12 is joined to the roll holder 16 via a thread 26. Ifthe clamping jig 12 is fastened securely to the pipe end 18, and if theroll holder 16 is rotated around the longitudinal axis L, the profilerolls 14 move on a helical path around the longitudinal axis L.

FIG. 2 shows the thread-rolling tool 10 in a section perpendicular tothe pipe longitudinal axis L.

FIG. 3 shows a detail view of a profile roll 14. It can be seen thatthis tapers conically in the present embodiment. By this it will beunderstood that an imaginary envelope body 28 in the form of a truncatedcone can be so fitted on the profile roll 14 that it contacts this alongits shell surface. The points of contact lie on concentric rings, sincethe profile roll 14 is pitchless.

FIG. 4 shows the thread-rolling tool 10 in a further perspective view.It can be seen that the roll holder 16 has a coupling structure 30,which in the present case is formed by a male hexagon structure. Thecoupling structure 30 is designed for interlocking interaction with awrench having complementary coupling structure.

A method according to the invention is carried out by the fact thatfirstly the thread-rolling tool 10 is fastened to the pipe end 18. Forthis purpose the thread-rolling tool 10 is inserted with its clampingjig 12 into the pipe end 18. Then the fastening connecting piece 24 isturned with a suitable tool, so that the jig 12 fastens thethreading-roll tool 10 on the pipe end 18. Then the roll holder 16 isrotated. This may be done, for example, by attaching an associatedwrench to the coupling structure 30 and turning it. Obviously it is alsopossible to use a drive, for example an electric, pneumatic or hydraulicdrive, for rotation of the roll holder 16.

In addition, a positioning machine, especially a machine tool or arobot, which comprises a thread-rolling tool according to the invention,is according to the invention. The positioning machine may be designedfor automatic insertion of the thread-rolling tool 10 into a pipe end18, for clamping of the clamping jig and for rolling of the roll holder16. If necessary, the positioning machine has a tool changer and/or aworkpiece changer, so that a plurality of pipes can be machined at theirrespective pipe ends by cutting a tapering thread, especially a conicalthread.

FIG. 1 shows a profile roll width B14 of the profile roll. When theprofile roll 14.1 is in contact over its full profile roll width B14with the thread that has just been rolled, the thread has a thread widththat corresponds to B14.

LIST OF REFERENCE SYMBOLS

-   10 Thread-rolling tool-   12 Clamping jig-   14 Profile roll-   16 Roll holder-   18 Pipe end-   20 Clamping element-   22 Clamping cone-   24 Actuating connecting piece-   26 Thread-   28 Envelope body-   30 Coupling structure-   D_(14.1) First profile axis of rotation-   D_(14.2) Second profile axis of rotation-   D_(14.3) Third profile axis of rotation-   L Pipe longitudinal axis

1. Thread-rolling tool for rolling and/or repairing a thread, with a) aclamping jig (12) for fastening to a pipe end (18) and b) at least oneprofile roll (14.1) for rolling a thread into the pipe end (18) or forrepairing a thread at the pipe end (18), wherein c) the at least oneprofile roll (14.1) tapers in a feed direction of the profile roll (14),so that a tapering, especially a conical thread can be rolled into thepipe end (18).
 2. Thread-rolling tool according to claim 1, wherein theprofile roll (14) is pitchless.
 3. Thread-rolling tool according toclaim 1, comprising a roll holder (16), on which the at least oneprofile roll (14.1) is fastened and by means of which the at least oneprofile roll (14.1) can be so guided helically around the pipe end (18)that the at least one profile roll (14.1) rolls a thread into the pipeend (18).
 4. Thread-rolling tool according to claim 1, wherein the rollholder (16) is coupled by means of a thread (26) with the clamping jig(12), so that a rotation of the roll holder (16) around a pipelongitudinal axis (L) of the pipe end (18) leads to an axial movement ofthe roll holder (16) along the pipe longitudinal axis (L). 5.Thread-rolling tool according to claim 1, comprising at least one secondprofile roll (14.2), which is so fastened to the roll holder (16) thatthe second profile roll (14.2), during rotation of the roll holder (16)around the pipe longitudinal axis (L), rolls at least partly in groovesrolled by the first profile roll (14.1) and wherein, in operation, itgenerates, in a direction at least partly opposed to a first passiveforce that acts on the first profile roll (14.1), a second passiveforce.
 6. Thread-rolling tool according to claim 5, wherein the firstprofile roll (14.1) is mounted to rotate around a first profile rollaxis of rotation (D_(14.1)) and a first offset angle between the firstprofile roll axis of rotation (D_(14.1)) and the pipe longitudinal axisamounts to at most 2°, especially at most 1° and/or the second profileroll (14.2) is mounted to rotate around a second profile roll axis ofrotation (D_(14.1)) and a second offset angle between the second profileroll axis of rotation (D_(14.2)) and the pipe longitudinal axis amountsto at most 2°, especially at most 1°.
 7. Thread-rolling tool accordingto claim 5, comprising at least one third profile roll (14.3), which isso fastened to the roll holder (16) wherein the third profile roll(14.3), during rotation of the roll holder (16) around the pipelongitudinal axis (L), rolls at least partly in the grooves rolled bythe first profile roll (14.1) and/or the second profile roll (14.2) andwherein, in operation, it generates a third passive force, whichtogether with the first passive force and the second passive forcepreferably adds up vectorially to zero.
 8. Thread-rolling tool accordingto claim 7, wherein the third profile roll (14.3) is mounted to rotatearound a third profile roll axis of rotation and the third profile roll(14.3) is mounted to rotate around a third profile roll axis of rotation(D_(14.3)) and a third offset angle between the third profile roll axisof rotation (D_(14.3)) and the pipe longitudinal axis amounts to at most2°, especially at most 1°.
 9. Method for producing or repairing aconical thread, with the steps of: (i) fastening a thread-rolling tool(10) according to claim 1 onto a pipe end (18) by means of the clampingjig (12) and (ii) rotating the roll holder (16), wherein the threadmoves the roll holder (16) axially along a pipe longitudinal axis (L) ofthe pipe end (18), so that the at least one profile roll (14) moveshelically around the pipe longitudinal axis (L) and rolls a conicalthread into the pipe end (18).
 10. Method according to claim 9, whereina thread is rolled with a thread width that corresponds at most to aprofile roll width (B₁₄) of a profiled shell surface of the profile roll(14).